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1-10 of 13 messages
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Help on a Los Angeles area RDF?
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by KG6YTZ on August 21, 2005
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For a few months now, I've been noticing an unmodulated signal on or around 145.21 MHz, perhaps 145.2125, which appears at night [about 10pm?] and disappears during the day [about 8am?]. I don't know what it is or where it is, but I'd like to know, especially since it causes a small amount of minor interference to the outputs of two repeaters and - worse than that - never identifies. It never does anything else, either, except come on at night and shut off in the morning. I've already gone into some detail about it on www.thunter.org, so rather than repost all that here, you can check the message board there.
I have no RDF equipment, not even a directional antenna - the only piece of hardware I could use to hunt it is my 2m HT. I believe, but cannot confirm, that it may be south of Pasadena and west of Temple City. That could place it somewhere around San Gabriel or Rosemead.
One of the users at thunter.org expressed some interest in hunting it, but it doesn't seem like he can fit a night hunt into his schedule. So, is there anyone else in this area who might be up for a night hunt, possibly around the San Gabriel Valley area? I'd like to get some experienced help with finding the source of this signal.
I can be reached at xfire905 [at] AOL.
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RE: Help on a Los Angeles area RDF?
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by N8NOE on October 4, 2005
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SAme type deal here in Michigan, Found it to be a Power Sub-Station Close by.. The station NEVER gave any trouble before so Everyone overlooked it.. Try teh Power Lines/Sub-Station/What you might have close... It's a thought..
Jeff-N8NOE
P.S. Our Comcast Cable is TERIBLE on 145.250, Cable leakage and they don't do a thing about it. But if you runn 500+w Mobile, and your close the The Office and antennas you get heard. I'm thinking the BPL thing would do the same..
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RE: Help on a Los Angeles area RDF?
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by WB6BYU on October 5, 2005
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There are lots of transmitter hunters in the LA area, so
that is a good place to start. But if you haven't been
able to get help tracking it down, I can help you build a
directional antenna (cheap) that you can use with your HT
to help find the source.
I'd come along myself, but I'm about 1000 miles to far away.
- Dale WB6BYU
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RE: Help on a Los Angeles area RDF?
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by KG6YTZ on June 19, 2006
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Just a quick [heh!] update...
One, the ham who had offered, almost a year ago, to help me track this signal was none other than the late N6IDF. He seldom had any opportunity to be out around my area, and he was never able to detect it on those few occasions when he happened to be passing through, so... No help there. N6IDF, silent key, 2006.
Two, I have decided that my fixed station's antenna - an indoor-mounted "portable ARES/RACES" 2m vertical dipole - needs upgrading. [Apartment dweller. Best I can do.] Toward that end, I've started putting together a simple dipole using a BNC-to-binding-post gadget [Pomona Electronics #1452, if you want to look it up] and a couple of lengths of unbent coathanger. I don't have a decent feedline for it yet, which is why it's unfinished, but I do have about six feet of RG-58 [?] with BNC's on both ends. This means that I now have something I can take mobile that IS both portable and directional [when held horizontally], so I can probably get some more accurate bearings with this than I can with any duck, though not as accurate as with, say, a Yagi.
I seem to have been correct in my assumption that it's west of my home. I haven't gone out a-huntin' with this little dipole yet, but while experimenting, I found that I could indeed null out the signal with it. I need to try from a few more locations, although I have tried to mobile DF it a couple of times before with my HT - most recently early last September, as I recall - and had no luck even detecting it. I have since installed an IC2100 in the car. Between that and the HT-dipole combo, I might at least be able to narrow down the general area of the source. I don't expect to be able to pinpoint it.
I also mentioned this signal on QRZ recently, and was contacted by an OOC [Official Observer Coordinator], so at least now they're aware of it too. I don't know whether anyone else has tried to find it, though. At any rate, the phantom signal remains active, generally following its usual pattern of showing up sometime during the night, never identifying or carrying any kind of audio or data that I've ever heard, and shutting down sometime during the day. [That's simplifying it a bit - this just seems to be the most common pattern.] I am more convinced than ever that its center frequency is 145.2125 MHz.
It is most definitely not a receiver birdie. Birdies do not show up at the same frequency on multiple receivers of different makes and models, do not appear and disappear, do not have directional bearings, cannot be nulled out, and cannot be attenuated. Something is radiating this signal. Could be just about anything. <shrug> I still suspect an origin somewhere around San Gabriel, though. It's not causing any truly serious interference that I'm aware of, but just the fact that it's a signal that goes for hours at a time with no apparent ID or purpose makes it worthy of attention IMHO.
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RE: Help on a Los Angeles area RDF?
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by WB6BYU on June 20, 2006
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You might ask Joe Moell K0OV for suggestions. His website
is www.Homingin.com, and he knows most of the transmitter
hunters in the greater LA area. Besides writing the
book on the topic and a regular column on DF for CQ VHF
magazine (and 73 magazine before that), he is the ARRL
DF coordinator (or some such title.)
Directional antennas are easy to make. My favorite for
getting started is a 2-element quad, though if the
signal is horizontally polarized a 3 or 4 element yagi should
work. The simplest construction method is the "cheap yagi"
approach of WA5VJB as shown here:
http://oldweb.clarc.org/Articles/uhf2.htm
which I make using thinwall PVC pipe instead of wood for
the boom.
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RE: Help on a Los Angeles area RDF?
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by K8MHZ on March 13, 2007
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Could be CATV. I get a carrier on 145.25 from our CATV system. Ours is coming from our own amp so I can turn it off when I need to. Last year it was more than that and I helped the CATV company RDF a bad amp in a house around 200 feet from here.
Trick: Use a 2 meter Yagi to get a heading. Once you get close use a 440 Yagi and reciever on 435.6375 and you should be able to get pretty close to the source.
By the same token have you listened on 48.40 to see if you are hearing a harmonic on 2 meters?
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RE: Help on a Los Angeles area RDF?
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by KG6YTZ on June 10, 2007
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Still no clue as to the source - what that means, basically, is that I don't know what it is, but I don't know what it ISN'T, either. I can't say that it isn't CATV leakage, deliberate interference, a harmonic of something, or whatever. Nothing has been ruled out yet, and almost nothing CAN be ruled out, although I have tried shutting off all of my circuit breakers and found that the signal was still present.
A couple of experienced local T-hunters have volunteered to help out - one is in Orange [N6UZS, not exactly nearby], and one is in Monrovia [KF6GQ, much closer]. They're not sure whether they're getting it, or exactly what frequency it's actually on. I'm not 100% sure about the frequency either, but I now think that it may be closer to 145.208. I haven't noticed it during the past few evenings, but if it shows up tonight, I'll give KF6GQ a call.
I have recently made contact with a "returning" ham in Arcadia [KE6MGB], just about two miles north of me, who says he is receiving it very strongly on his VX-7R as well. And he brought it up first - I hadn't mentioned it to him beforehand - so there's the witness I needed. At least now I know that it is in fact detectable from other locations as well. No bearing known from his location yet.
If/when we ever get this mystery solved, I'll definitely let you guys know...
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RE: Help on a Los Angeles area RDF?
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by WB6BYU on June 11, 2007
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I helped to track down some CATV interference in a small town here in
Oregon recently. We DF'ed it to some power poles, but couldn't tell
whether it was from the CATV wires or controllers for the street lights
that were on the same poles. What really cinched it, however, was to
put a wide-band FM receiver on 149.8 MHz (or thereabouts). Not many
street light controllers will be broadcasting Oprah!
(That is the sound channel that goes with the video on 145.25 MHz
or thereabouts. A spectrum analyzer also comes in handy - when I
parked under a pole and saw pairs of spurs come up on the display
every 6 MHz between 120 and 170 MHz, it ws pretty obvious what
the source was.)
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RE: Help on a Los Angeles area RDF?
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by KG6YTZ on June 16, 2007
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Well, here's how things seem to have turned out...
KF6GQ could not detect this signal while he was driving toward my home this past Sunday evening. He did, however, note many weak signals on or near the same frequency, and actually had to sniff around my apartment building before he could get a fix on it. He says that what I am getting at home, what I get at work in Pasadena, and what KE6MGB is getting in Arcadia ARE NOT THE SAME SIGNAL. I have to admit I'm surprised, but the evidence seems to add up.
It seems that what I am getting at home appears so strong on any rig connected to my indoor vertical dipole because the source is right next door. Somewhere in Apt. 8 - which, by the way, IS indeed west of my apartment! - something is leaking. I don't know what, and I don't know why it would come and go like it does, but KF6GQ says that tiny little phantoms like these are common, especially around this frequency. Even then, he says, it's still not a particularly strong signal - it only showed a strength of 2 [out of 9?] on his sniffer from outside that apartment. It's got to be very close to my dipole. Not directly adjacent to it - there's a closet between here and there, for one thing - but perhaps within a few feet of it.
I've never talked to that neighbor; I don't even know whether she speaks English. I have no idea whether I'll ever get a chance to zero in on the offending whatever-it-may-be.
Mystery ALMOST solved... <shrug>
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RE: Help on a Los Angeles area RDF?
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by WB6BYU on June 17, 2007
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There are LOTS of 2m signal sources around, particularly from digital
equipment of various types. I also have problems with battery chargers,
alarm systems, and other devices. Often the first signal I locate with
a new DF receiver is my fax machine.
One solution is to move your antenna to the other side of the room,
putting it further from the noise source. If it is still a problem you can
try an antenna with a sharp null in that direction - it won't knock it
out entirely, but may be enough to make it usable.
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